Thermostat Blue Drain Plug - Different than Block?

LUnaCY

Active Member
Aug 28, 2018
206
Afton, MN
Boat Info
310 Sundancer 2002
Engines
Mercruiser 5.0 MPI Bravo III
I have 2002 Mercruiser 5.0 MPI sterndrives. Winterinzed it today and had an issue with 1 thermostat drain plug. It seems the thermostat drain plugs are different size than the 3 block drain plugs. Does anyone have a part number for these? I purchased a replacement block drain plug and it didn't fit (18-4226). One of my tstat drain plugs works great on both engines, and the previous owner "made" the wrong one fit on the other engine.
 
As far as I know, they are the same. HOWEVER, I have the same issue. My thermostat drain plug doesn’t fit well in the other spots.

I just make sure to use the same plug for the thermostat housing and not try to put it into the water distribution fitting down low.
 
Figured it out. They are different on my boat. Manifold/thermostat drain plug is part #22_806608A1.
 

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